1. Field of the invention
This invention relates to an improvement of an image processing equipment of a copying machine or a printer for instance, by which the image density setting conditions can be adjusted according to the temperature change of a photosensitive body and more particularly relates to an image processing equipment by which a beautiful image density can be secured at all times by selectively determining proper image density setting conditions even in the case that such an irreversible characteristic deterioration of a photosensitive body as electrification power, sensitivity, etc. occurs.
2. Description of the Prior Art
There are some of photosensitive bodies utilized in an image processing equipment, of which such an characteristic as electrification power, etc. may change according to the temperature. For this reason, a copying equipment in which the characteristic changes accompanied with the temperature change of a photosensitive body can be detected by accumulatively calculating the copy processing time to cause such image density setting conditions as voltage, etc. given to an exposure lamp to be changed has been already known to those skilled in the art (refer to, for instance, the Japanese Laid-open Pat. Pub. No. Sho-63-191161).
In such a conventional art, as the image density setting conditions are changed according to the changes of the characteristic due to the temperature changes of the photosensitive body, it is excellent in the point of securing a constant image density, not depending upon the temperature changes of the photosensitive body.
Thus, in a copying equipment disclosed by the Japanese Laid-Open Pat. Pub. Sho-63-191161, the image density is kept constant by, for instance, lowering (increasing) the voltage of an exposure lamp according to increase (or decrease) of the temperature of a photosensitive body. Therefore, such a control method as shown in the above can correspond to so-called reversible changes i.e., the characteristic of the photosensitive body returns to the original state thereof as the temperature of the photosensitive body returns as before. However, it can not correspond to the case that the characteristic of the photosensitive body changes irreversibly.
Such irreversible changes of the characteristic for the temperature of the photosensitive body as shown in the above are remarkable in the case of an organic photosensitive body. For instance, even though the temperature returns to the original level thereof if the organic photosensitive body is intermittently or consecutively exposed to a temperature exceeding 50.degree. C. for more than an appointed period of time, it is known that the relationship between the temperature and the characteristic does not return as before, i.e., it shows irreversible changes.
And in the case that the relationship between the temperature and the characteristics of a photosensitive body changes irreversibly as shown in the above, letting the image density setting conditions strictly follow accompanies complication of softwares and large scale of the capacity of a memory device in the present time when such a technology as to carry out universal control by applying a micro computer has been developed, and it necessarily results in increase of the production cost.